Fault in Auxiliary Transmission Control Module
The auxiliary transmission control module has detected a fault.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The transmission control system has noticed a problem with the auxiliary control module, which could affect how the transmission responds or shifts.
What the computer is actually seeing
The auxiliary transmission control module monitors various parameters like shift timing, pressure signals, and control inputs. When it detects an error in its system voltages (typically between 0.5V-5V for signals) or if it cannot communicate properly (CAN bus error), it triggers this fault.
What a healthy reading looks like
Expected signal voltages from the auxiliary control module under normal operation: 0.5V to 2.5V for low signals, 2.5V to 5V for normal signals; typical CAN bus communication rates are 500 Kbps.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Check wiring and connectors between the ECM and the auxiliary transmission control module for damage or corrosion. Decision: Is wiring intact? (Yes: go to step 2, No: repair wiring)
- 2Inspect the transmission fluid level and condition. Decision: Is fluid level sufficient and clean? (Yes: go to step 3, No: top off or replace fluid)
- 3Use a scan tool to check for additional DTCs that might indicate other faults. Decision: Are there other related codes? (Yes: address those codes, No: go to step 4)
- 4Check the operation of the auxiliary transmission control module by measuring signal voltages while performing a transmission shift. Decision: Are voltages within expected range? (Yes: module functioning, No: replace auxiliary transmission control module)
Common causes
- Wiring issues (frayed or shorted wires)
- Faulty auxiliary transmission control module
- Corrosion in connectors
- Low transmission fluid level
- Signal interference on the CAN bus
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's better to limit driving until the issue is resolved; it can cause transmission problems.
Will this code clear on its own?
Not likely. The issue needs to be addressed for the code to clear.
What happens if I ignore this code?
Ignoring it can lead to transmission failure or damage, increasing repair costs.
Working a real vehicle right now?
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